High pressure vessels are typically fabricated in a single piece construction using, for example, steel, or are welded together to prevent leakage. Conventional methods of producing high pressure vessels include rolling the material into a desired shape and often forging parts that are welded together. Some mechanical properties of steel may be adversely affected by welding, unless special precautions are taken. Using welding to manufacture high pressure vessels introduces point of failure as well as increasing the time and cost of producing high pressure vessels.
Some high pressure vessels are used as diaphragm accumulators. These accumulators are typically made of steel. They are traditionally of two distinct designs: threaded and welded. The former design allows for replaceable/serviceable diaphragms, while the latter does not. In both design variations, thick steel shells are mated together with a diaphragm captured in between, typically in the proximity of the threaded or the welded joint. The steel shell supports the structural load arising from the internal pressure. In the threaded version, the two halves are machined for threads and seal interface. The pressure sealing of the accumulator at the threaded joint is achieved by compression or securing the elastic diaphragm periphery close to the threaded joint. The fluid and gas ports are either integral to the shell or welded on to them using a secondary traditional welding process.
In the welded version, the two sections of the shell are manufactured using casting, forging or machining followed by weld at the seam. The halves are welded using laser or electron beam to avoid heat ingress inside the shell that can damage the diaphragm. In most legacy diaphragm accumulators of welded kind, the diaphragm is held in place during mating of the two halves at the equator using a metal clip that prevents the diaphragm from slipping inside the inside surface.
Some accumulator manufacturers have attempted to reduce weight of diaphragm accumulators by substituting steel with lighter and/or stronger materials, such as aluminum, titanium or brass and reducing the wall thickness of the shell. Other attempts to produce lighter diaphragm accumulators include replacing the steel shells (cylinder with domes) with aluminum, welding the two aluminum halves and overwrapping them with composite material. However, there has been limited effort in designing diaphragm accumulators that does not require welding or threading altogether.
Because welding or threading adds to the complexity and time to production of high pressure vessels in general and diaphragm accumulators in particular, it is desirable to produce a high pressure vessels or diaphragm accumulators without the use of welding or threading. Furthermore, as high pressure vessels find use in a wide variety of application, such as diaphragm accumulators in robotics, automobiles, aircrafts, prosthetics, pulsation dampeners, etc., it is desirable to produce high pressure vessels that are significantly lighter in weight yet providing the same or greater pressure gradient without the need for welding.